Actually, you can and should send out your transcripts to AMCAS now. They began accepting transcripts around May 1st. Your transcripts will be held at AMCAS, assuming they don't lose them 😡 , until your application is submitted. This way, they can begin verifying your application right away once your application is received. The sooner they verify your course work, the sooner they'll send your application out to all your schools.
The AMCAS web application has a section where it will generate a form that you will print out and give to the transcripts office at your school. The process of sending the actual transcript to AMCAS is specific to your own school so figure that out first. In addition, each transcript sent to AMCAS must be accompanied by this special form that you printed out.
Believe me, as a second time applicant getting things in early is a major key to this whole process. Unfortunately I learned that lesson the hard way the first time around (late application, August MCAT) so get those transcripts out soon.
Good luck. 🙂